Water storage tank



FIG. 1 is a front view of a water storage tank, showing my new design;

FIG. 2 is a rear view of the water storage tank in FIG. 1;

FIG. 3 is a right side view of the water storage tank in FIG. 1;

FIG. 4 is a left side view of the water storage tank in FIG. 1; and,

FIG. 5 is a top plan view of the water storage tank in FIG. 1. 

I claim the ornamental design for a water storage tank, as shown and described. 